If you thought the amount of scoring in the NFL’s Week 1 games was less than usual, you were right in a big way. A total of 21 teams scored less than 20 points in the 16 games — that number was the highest total of Week 1 sub-20-point team scoring since the 1970 AFL-NFL merger, according to research through Pro-Football-Reference.com.

The 21 teams was a far cry from last season’s Week 1 total of only 14 teams. In the decade of the 2000s, 153 teams scored under the 20-point mark in Week 1, an average of 15.3 per season. Since the NFL expanded to 32 teams and eight divisions in 2002 for 16 opening weekend games, the average was 15.25 per season from 2002-09.

There are a lot of factors at play in why this was the case in this particular opening weekend. Better defenses, weather issues and injuries to key players certainly played a part. But one other factor might also be in play.

The last time most clubs play their starters for an appreciable time in the preseason is Week 3. Most clubs hold out starters or play them very little (one or two series) in the final week in order to look at players fighting for the final spots during the remainder of the game.

It’s almost a bye week for the starters on both sides of the ball, since they will not face live competition for two weeks until the regular season starts. So, when the starters get back on the field in Week 1 of the regular season, the timing is off when it needs to be at its sharpest.

Here are the year-by-year totals of Week 1 teams at or under 19 points in the decade of the 2000s.